Fine tuning drive which clutches automatically on slight
turning of vernier knob and declutches
automatically on excessive turning



Jan. 20, 1970 w. l.. FULTON FINE TUNING DRIVE WHICH CLUTCHESAUTOMATICALLY ON SLIGHT TURNING OF VERNIEH KNOB AND DECLUTCHESAUTOMATICALLY ON EXCESSIVE TURNING Original Filed June 27, 1961 5Sheets-Sheet 1 Jan. 20, 1970 w. L, FULTON Re. 26,777

FINE TUNING DRIVE WHICH CLUTCHES AUTOMATICALLY ON SLIGHT TURNING OFVERNIER KNOB AND DECLUTCHES AUTOMATICALLY ON EXCESSIVE TURNING OriginalFiled June 27, 1961 5 Sheets-Sheet a Jan. 20, 1970 w. l.. FULTON Re.26,777

FINE TUNING DRIVE WHICH CLUTCHES AUTOMATICALLY ON SLIGHT TURNING OFVERNIER KNOB AND DECLUTGHES AUTOMATICALLY ON EXCESSIVE TURNING OriginalFiled June 27, 1961 5 Sheets-Sheei 1 /42 INVENTOR,

,fa/1.4mm fm/@a Farfa/y Jan. 20, 1970 w. FULTON Re 26,777

FINE TUNING DRIVE WHICH CLUTCHES AUTOMATICALLY ON SLIGHT TURNING OFVERNIER KNOB AND DECLUTCHES AUTOMATIGALLY ON EXCESSIVE TURNING OriginalFiled June 27, 1961 5 Sheets-Sheet 4 Jan. 20, 1970 w. l.. FULTON Re.26,777

FINE TUNING DRIVE WHICH CLUTCHES AUTOMATICALLY ON SLIGHT TURNING 0FVERNIER KNOB AND DECLUTCHBS AUTOMATICALLY ON EXCESSIVE TURNING UriginalFiled June 27, 1961 5 Sheets-Shee'f f United States Patent O FINE TUNINGDRIVE WHICH CLUTCHES AUTO- MATICALLY N SLIGHT TURNING OF VERNIER KNOBAND DECLUTCHES AUTOMATICALLY ON EXCESSIVE TURNING William LeonardFulton, Roselle, Ill., assignor to Standard Kollsman Industries, Inc.,Melrose Park, Ill., a corporation of Illinois Original No. 3,248,674,dated Apr. 26, 1966, Ser. No.

403,690, Oct. 2, 1964, which is a continuation of application, Ser. No.119,377, June 27, 1961. Application for reissue Apr. 22, 1968, Ser. No.735,474

Int. Cl. 1103i /02 U.S. Cl. 334-51 9 Claims Matter enclosed in heavybrackets appears in the original patent but forms no part of thisreissue specification; matter printed in italics indicates the additionsmade by reissue.

ABSTRACT 0F THE DISCLOSURE A preset fine tuning arrangement, whichincludes a separately gear driven slug for tuning each of the channels,and the slug is automatically disengaged from the gear drive at the endsof its stroke.

This invention relates to novel fine tuning mechanisms, particularly fortelevision tuners, of effective, simplified and economical construction;and is a continuation of my U.S. Patent application Serial No. 119,877,filed June 27, 1961, for Fine Tuning Mechanism, now abandoned.

The band-width of television channels is six megacycles. There aretwelve VHF channels, which generally are tuned-in through individual ordiscrete steps. The common circuit sections of the tuner are therebyaltered to tune to the desired channel frequency band. As the requisiteoscillator frequencies for the signal heterodyning should be close topredetermined values, a common manual fine tuning element has generallybeen provided for this purpose. However, whenever such element isadjusted for one channel, it upsets the setting for the others.

Recently, relatively complex twelve-position camming devices have beenintroduced to avoid such resettings, utilizing individual presettablefine tuning cams for the channel selection positions of the tuner. Theirutility has been particularly indicated in motorized remote tuningtelevision receivers. Permitting individual channel tine tuning throughexternal adjustment by a single knob, troublesome retuning of the otherchannels was avoided. However, the added weight, cost, space, andmechanical vulnerability of such devices have limited their general usein television receivers.

In accordance with the present invention, a single control pinion isoperated through the external ine tuning knob, to selectively operatethe oscillator coil slugs directly for all the television channels` Thecontrol pinion is rotatable in either direction, to effect tinelongitudinal adjustments on any engaged slug, and thereby precisely tunethe circuit for the selected channel. Upon manual release of the knob,internal resilient biasing of the invention mechanism directlydisengages the control pinion. The oscillator slugs are thus retained intheir individual settings for normal tuning-in operations by the tuner.Should any channel later require returning its presettable slug isdirectly reset simply by turning the ne tuning knob. Visual observationof this operation is available on the screen, as precise tuningpresetting occurs with best picture reception.

The invention preset ne tuning mechanism is simple in construction,contains relatively few parts, and is rugged. Its compactness andeconomy make it practical Reissued Jan. 20, 1970 for general televisionuse. The preferred application is to directly control any of theoscillator coil slugs of the tuner, and thus eliminate the need for acommon fine tuning impedance as heretofore employed. The oscillatorslugs hereof are in the form of threaded metal members or screws. Eachslug has a transverse head formed as a gear and engageable with thecontrol pinion. The slug head gears are moved to be out of engagementwith the pinion, at either end of their stroke.

It is accordingly a primary object of the present invention to providenovel tine-tuning mechanism, individually presettable in tuners withdiscretely tuned television channels.

Another object of this invention is to provide novel presettable netuning mechanism of simplified and rugged construction.

A further object of this invention is to provide novel presettable netuning mechanism of direct and precise operation; and directlydisengaged when the external knob is released through internal biasing.

Still another object of this invention is to provide novel presettablefine tuning mechanism that inherently avoids damage to the oscillatorslugs, or freezing of the mechanisrn at the end positions of the slugs.

These and other objects of this invention will become more apparent fromthe following description of an exemplary embodiment thereof,illustrated in the drawings, in which:

FIG. l is a side elevational view of a tuner, embodying a form of thisinvention.

FIG. 2 is an end elevational view of the FIG. 1 tuner, showing theexterior preset mechanism portion in face vlew.

FIG. 3 is an enlarged cross-sectional view, longitudinally through thepreset mechanism of FIG. 1 when in its neutral position.

FIGS. 4 and 5 are respective cross-sectional views through the camsection of the FIG. 3 mechanism, taken along the lines 14-14 and 15-15thereof.

FIG. 6 is a cross-sectional view of the preset mechanism correspondingto FIG. 3 when in the clockwise knob ne tuning mode.

FIGS. 7 and 8 are respective enlarged cross-sectional and face views ofthe cam section of FIG. 6 taken along lines 17--17 and 18-18 thereof.

FIG. 9 is a cross-sectional view of the preset mechanism correspondingto FIG. 3, when in the counterclockwise knob tine tuning mode.

FIGS. 10 and ll are respective enlarged cross-sectional and face viewsof the cam section of FIG. 9, taken along the lines 14-14 and 15-15thereof.

FIG. l2 is a perspective view of the actuating cam member.

The VHF television tuner, illustrated in FIGS. l-Il, embodies apreferred form of the present invention for selectively presetting theoscillator slugs by external manual operation of the fine tuning shaft.Tuner utilizes typical RF circuitry including an RF amplifier tube 101and oscillator-mixer tube at 102. A box-like metal chassis 103 enclosesand shields a rotatable turret or drum 105 manually operated by selectorcontrol shaft 106. An antenna input network board 104 connects to theantenna lead-in. A separable front cover 108, and side-bottom cover 109,complete the overall shielding and protection of internal parts.

The drum 10S is composed of individual panels 110 longitudinallyarranged across mounting discs, in a suitable conventional manner. Acentral disc 111 is advantageously used, as both a circuit shield anddetent plate in the manner of U.S. Patent 2,496,183 which issued onJanuary 31, 1950 and assigned to the same assignee.

Each panel 110 contains circuit elements, as coils, that are selectivelyconnected into the fixed tuner circuitry through contacts 112, 112 (FIG.3) on the panels, in the well known manner.

The oscillator coil (114) at the left end of each panel 110 (see FIG. 3)has a metallic slug 115 suitably threaded into the end of the panel(110) body, and is longitudinally displaceable in the coil 114 forpresetting its circuit frequency. Each slug 115 contains a transverseheadgear 116 at its exterior end. The control pinion 120 is engaged witha positioned slug gear 116 through turning of fine tune hollow shaft 107in either the C.W. or C.C.W. direction. The pinion shaft 121 containsdriven gear 122 which is engaged with drive gear 123; schematicallyrepresented in dotted lines in FIG. 1.

A biasing spring 124 presses against gear 122 and moves the pinionfdrivegear assembly 124, so that pinion 120 becomes disengaged from the sluggears 116 upon release of shaft 107, for the neutral mode. Theslipclutch-cani assembly 130 is pressed Onto fine tune shaft 107 by ametal band 131. Its cam section 135 extends transversely outwardly andcoacts with pinion shaft 121. Shaft 121 is held in coaction with cam 135by a C spring 136, as will be set forth hereinafter. The coacting shaftend engages a hollowed-out cam 138 in cam section 135, indicated indotted lines in FIG. 2.

FIG. 3 shows the preset ne tune mechanism 140` for the tuner 100 in itsneutral mode, which occurs while the fine tune knob 137 on shaft 107 isreleased. The C spring 136 is hooked onto a projection 139 of cam body135, and about the end 121' of control shaft 121 at cam 138. Spring 136thereupon tilts shaft 121, with gear 122 pivoting on drive gear 123,thereby disengaging control pinion 120 from slug gears 116. The camfollower end 121' of control shaft 121 is forced against the apex 141 ofthe inverted V cam 138 surface of the clutch-cam member 130; see FIGS. 4and 5. Such angular displacement of control pinion shaft 121 is amechanically positive action in the control mechanism 140 hereof.

Further, the biasing spiral spring 124 presses against gear 122. andmaintains shaft end 121' stably in cam 138 during the neutral mode. Theslug 115 of the positioned panel 110 retains its longitudinal positionlast longitudinally preset with respect to its oscillator coil 114. Aflat retaining spring 144 holds the slug 115 firmly in its presetpositions in the dielectric panel 110. The oscillator end of panel 110is suitably held in end mounting disc 117 of the drum 105. Whileindividual removed panels (110) are used in tuner 100, it is to beunderstood that the preset mechanism 140 may be used with non-removablecircuit elements and slugs (115).

The control mechanism gears 120, 122 and 123 are desirably made of toughand resilient plastic material, as is member 130. The control shaft 121is arranged to freely pivot, with its left bearing 145 in cover plate108 and aperture 146 in chassis wall 103 being adapted for this purpose.During the tilting and displacement (to the left) of the control shaft121 to the neutral position illustrated in FIG. 3, spur gears 122 and123 remain engaged. The control operation modes of mechanism 140 retainssuch gear engagement for the slug 115 presetting actions, as will now bedescribed.

The resilient plastic material of gears 122, 123 permits smoothtransition among the three operational modes, despite their angular andlongitudinal displacements. In practice, the angular tilt of gear 122,to keep control pinion 120 clear of the head-gears (116) in the neutralmode, need not be more than the order of The tilt angle for shaft 121 ispredetermined by the height of apex 141 of the inverted V carn 138,shown in crosssectional FIGS. 4 and 5.

FIG. 6 illustrates the control mode for preset mechanism 140 when finetune knob 137 is rotated in the C W. direction. Slip-clutch 130 isthereupon turned in the C.W. direction, with its cam 135 abutting camfollower end 121 of shaft 121, as shown in face view FIG. 8. The camsurface 138 thus presses follower 121' to cam control shaft 121 into thehorizontal position, and control pinion 120 also engages the positionedslug-gear 116. The clutch member 130 then slips with respect to shaft137 while the latter is continued in rotation. For this mode, the cam138 is shaped deepest at region 142. Control shaft 121 is thus displacedto the left by compressed spiral spring 124 to fully seat into camregion 142.

The CW. rotation of line tune knob 137 causes drive gear 123 to rotatedriven gear 132 in the C.C.W. direction. The control shaft 121 andcontrol pinion therefore turn in unison with gear 122. The positionedslug-gear 116 is thus rotated GW. while knob 137 is turned CW., asindicated by the arrows, in FIG. 6. Slug is arranged to movelongitudinally inwards of panel 110 when rotated C`.W., as arrow sshows. Continued rotation of control pinion results in spur gear 116"riding off" its edge, being the end of its inwardly stroke.

The displacement of pinion 120 to the left, through cam region 142,insures a safe clearance of pinion 120 with respect to such stroke limitof gears 116. This prevents overdrive and damage to the gears 116 andthe control mechanism 140. Upon release of knob 137, C. spring 136automatically presses cam follower 121 into the cam apex 141, tiltingconntrol shaft 121 and pinion 120 clear of the gear (116) paths and toneutraL FIG. 9 illustrates the C.C.W. control mode of preset mechanism140. When knob 137 is turned C.C.W., clutch-cam assembly I is initiallyrotated from neutral, until the cam follower tip 121 engages theshallowest edge 143 of the inverted V cam 138. The control shaft 121 ispositioned horizontally in the same manner as in the CW. mode described.However, shaft 121 is displaced to the right by shallower cam surface143 as shown in enlarged detail in FIGS. 10 and 1l, and denoted in FIG.9. The pinion 120 thereupon engages the positioned slug gear 116 andturns it in the C.C.W. direction, as indicated by the arrows.

The C.C.W. rotation of gears 116 motivates them in the outwardlydirection of panels 110, as indicated by arrow t. Continued rotation ofpinion 120 results in gear 116 riding off control pinion 120, over itsleft edge. This action safely disengages the slug gears (116) at the endof their outwards stroke. Release of knob 137 again returns the pinionto its tilt-off position of FIG. 3. Turning the fine tune knob C.W.shifts the pinion to the left of its FIG. 9 C.C.W. position, as seen inFIG. 6. Gears 116 at their outward stroke end are nevertheless engagedby the pinion of an inwards displacement upon C.W. rotation of knob 137.Similarly, gears at their inward stroke end are reengaged when the CCW.control mode is used.

FIG. l2 is a perspective view of cam means 28, with forward projection139 purposely deleted so as not to obscure the internal shape of theV-shaped cam surface. The V-shaped opening into which cam follower end121' projects is of a variable depth, consistent with the crosssectionalviews, as for example shown in FIGS. 4 and 5. Thus, in the normal restposition (of FIGS. 3-5) wherein cam follower end 121' is located at theapex of the V-shaped cam slot, it will project into said cam slot by thedistance indicated as arrow B.

When it is desired to move slug 119 inward, the tine tuning controls areas shown in FIGS. 6 8, wherein cam follower end 121' will now be locatedin the deepest region 142 of the cam slot, with the depth thereof beingindicated by arrow A. Continued rotation of the control pinion 120 movesslug 115 inward, with the length of gear members 116, 120 beinginterrelated to the depth of the cam slot, such that spur gear 116 willride off the edge of pinion 120 at the end of its inward stroke.

Although the present invention has been illustrated with exemplaryembodiments, it is to be understood that variations and modificationsthereof may be made by those skilled in the art, that fall within thebroader spirit and scope of the invention, as set forth in the followingclaims.

The embodiments of the invention in which an exclusive privilege orproperty is claimed are defined as follows.

l. A television tuner having a plurality of channel selection positionsindividually selectable through rotation of the channel selector shaft,a coil arranged at each of said channel positions for tuning of theassociated tuner channel circuitry, a slug for each of said coilsarranged about the axis of said selector shaft and mounted foradjustable inductance coaction with its associated coil, said slugsbeing individually longitudinally displaceable, gear means affixed toeach of said lugs at the exterior end thereof, a preset tuning shaft forindividually adjusting the tuning position of said slugs with theirrespective coils, drive gear means engageable with the respective sluggear means of the coil positioned for the selected channel, said drivegear means being disposed and supported radially from said preset tuningshaft, and mechanism coupled to said preset tuning shaft for rotatingsaid drive gear means and engaging it with the positioned slug gearmeans in either rotational direction and thereby controllablydisp1ac[e]ing the slug of the positioned coil in either longitudinaldirection, said mechanism including biasing means for normally holdingsaid drive gear means disengaged for said slug gear means while saidpreset tuning shaft is released, whereby the tuner channel circuits areheld tuned corresponding to the slug positions preset through saidpreset tuning shaft and mechanism and channel selection by said selectorshaft is unhindered, in which said mechanism includes a clutch coupledto said preset tuning shaft and a cam means motivated by said clutch[and containing a cam surface], [a] cam follower means coupled to saiddrive gear means, said cam [surface] means coactable with said camfollower means to displace the cam follower means and bring said drivegear means into driving engagement with said slug gear means againstsaid [the] biasing means upon rotation of said preset tuning shaft ineither direction, said biasing means directly moving sad cam followermeans to a position [in said cam] effecting said disengaged relationshipbetween said drive gear means and slug gear means upon release of saidpreset tuning shaft, said mechanism further including resilient meansfor axially displacing said cam follower into coaction with said cam[surface] means, said cam [surface] means being proportioned to axiallyposition said drive gear means to permit the slug gear means todisengage therefrom when its associated slug is at the end of its strokein either direction and to reestablish engagement with said disengagedslug gear means when operated in the opposite direction.

2. A television tuner having a plurality of channel selection positionsindividually selectable through rotation of the channel selector shaft,an oscillator coil arranged at each of said channel positions for tuningof the associated tuner channel circuitry, a slug for each of said coilsarranged concentrically about the axis of said selector shaft andmounted for inductive coaction with its associated coil, said slugsbeing individually longitudinally displaceable within said coil along apath parallel to said selector shaft axis, a gear aflixed to each ofsaid slugs extending transversely thereof at the exterior end thereofperpendicularly to said axis, a preset tuning shaft concentric with saidselector shaft for individually adjusting the ne tuning position of saidslugs with their respective coils, a control pinion engageable with therespective slug gear of the coil positioned for the selected channel,said control pinion being disposed radially from said preset tuningshaft, and mechanism operated by said preset tuning shaft for rotatingsaid control pinion and engaging it with the positioned slug gear ineither rotational direction and thereby controllably displac[e]ing theslug of the positioned coil in either longitudinal direction, saidmechanism including biasing means for normally holding said controlpinion from said slug gear while said preset tuning shaft is released,whereby the tuner channel circuits are held tuned corresponding to theslug positions preset through said tuning shaft and mechanism andchannel selection by said selector shaft is unhindered thereby, in whichsaid mechanism includes a slip clutch coupled to said tuning shaft and acam motivated by said slip clutch and containing a cavity cam surface, acam follower coactable with said cam surface and coupled with saidcontrol pinion, said cam surface being proportioned to displace [the]said cam follower and bring said control pinion into driving engagementwith said slug gear against the biasing means [hold] upon rotation ofsaid preset tuning shaft in either direction, said biasing meansdirectly moving said cam follower to a position in said cam effectingsaid disengaged relationship upon release of said tuning shaft, andresilient means for axially displacing said cam follower into coactionwith said cam surface, said cam surface being proportioned to axiallyposition said control pinion to permit the slug gear to disengagetherefrom when its associated slug is at the end of its stroke in eitherdirection and to reestablish engagement with such disengaged slug gearwhen operated in the opposite direction.

3. A television tuner having a plurality of channel selection positionsindividually selectable through rotation of the channel selector' shaft,a coil arranged at each of said channel positions for tuning of tlzeassociated tuner channel circuitry, a slug for each of said coilsarranged about the axis of said selector shaft and mounted foradjustable inductance coaction with its associated coil, means forthreadably retaining said slugs for individual longitudinal displacementwithin their respective coils and for maintaining the preset slugposition, gear means afxed to each of said slugs at the exterior endthereof, tt preset tuning shaft for individually adjusting the tuningposition of said slugs wit/1in their respective coils, drive gear meansengageable with the respective slug gear means of the coil positionedfor the selected channel, said drive gear means being disposed andsupported radially from said preset tuning shaft, and mechanism coupledto said preset tuning shaft for rotating said drive gear means andengaging it with the positioned slug gear means in either rotationaldirection and thereby controllably displacing the slug of the positionedcoil along said threadalily retaining means in either longitudinaldirection, said mechanism including biasing means for normally holdingsaid drive gear means disengaged from said slug gear means while saidpreset tuning shaft is released, whereby the tuner channel circuits areheld tuned corresponding to thc longitudinal slug positions, presetthrough said preset tuning shaft and mechanism and channel selection bysaid selector shaft is unhindered, said threadably retaining meansproviding longitudinal translation of said slugs within their respectivecoils lo define a stroke lengt/1 between predetermined first and secondend extremes, and means for longitudinally shifting said drive gearmeans such that said slug gear means is disengaged there rom when itsassociated slug is at said end extremes of its stroke and the rotationalinput of said preset tuning shaft is continued in the same rotationaldirection, and for reestablishing engagement with said disengaged sluggear means when said preset tuning shaft is rotated in the oppositedirection.

4. A television tuner, as set forth in claim 3:

said means for longitiudinally shifting said drive gear means includingmeans responsive to the direction of rotaion of said preset tuning shaftfor positioning said drive gear means at a ,rst longitudinal positioncorresponding to rotation of said preset tuning shaft in a )rstdirection, and at a second longitudinal position corresponding otrotation of said preset tuning shaft in a second direction, said firstrotational direction rotating said slug gear means through .saidmechanism and drive gear in a direction to provide inward longitudinalmovement of its associated slug along the threadably retaining means ofits coil, said second rotational direction rotating said slug gear meansin the opposite direction to provide outward longitudinal movement ofits associated slug along the threadably retaining means, said firstlongitudinal position of said drive gear means being longitudinallyoutward with respect to said second longitudinal position.

5. A television tuner as set forth in claim 4:

said drive gear means including a pinion of a predetermined longitudinalextent between an inward first end and an outward second end, said sluglgear means longitudinally translating along the lengtlz of said pinionduring rotational driving engagement thereof, said first end extreme ofsaid slug within its coil being the inward end of the stroke and saidsecond end extreme being the outward end of the stroke, the longitudinalextent and longitudinal shifting movement of said pinion beingoperatively related to the length of slug stroke, such that said sluggear means rides H said rst end of the pinion at said first end of itsinward stroke, while said pinion is positioned at said secondlongitudinally outward position, and said slug gear means rides off saidsecond end of the pinion at said second end of its outward stroke whilesaid pinion is positioned at said first longitudinally inward position,the longitudinal shifting of said pinion between said ytrst and secondlongitudinal positions being sufficient to reestablish engagement withsaid pinion and said slug gear means when said preset tuning shaft isoperated in the opposite direction.

6. A television tuner, as set forth in claim 3, further includingcomming means, said camming means including cam means motivated byrotation of said preset tuning shaft and cooperative cant follower meansoperatively connected to said drive gear means, said camming meansoperating against said biasing means for radially bringing said drivegear means into engagement with the slug gear means of the selectedchannel, and longitudinally shifting said drive gear means when therotational input to said preset timing shaft is reversed.

7. A television tuner as set forth in claim 4, further including cammingmeans, said cumming means including cam means motivated by rotation ofsaid preset tuning shaft and cooperating cam follower means operativel vconnected to said drive gear means, said camming means operating againstsaid biasing means for radially bringing said drive gear means intoengagement with the slug gear means of the selected channel, andlongitudinally shifting said drive gear means between said first andsecond longitudinal positions when the rotational input to said presettuning shaft is reversed.

8. A television tuner as set forth in claim 6, further including a slipclutch means coupling said cam means to said preset tuning shaft.

9. A television tuner having a plurality of channel selection positionsindividually .selectable through rotation of the channel selector shaft,a coil arranged at each of said channel positions for tuning of theassociated tuner channel circuitry, a slug for each of said coilsarranged about the axis of said selector shaft and mounted for axiallyadjustable inductance coaction with its associated coil, means forthreadably retaining said slugs for individual longitudinal displacementwithin their respecti ve coils and for maintaining the preset slu gposition, slug gear means affixed to each of said slugs at tlze outerend thereof, preset tuning mechanism selectively engageable with theparticular tuning slug at the tuning position for individually adjustingthe axial position of such slug between predetermined first and secondend extremes, said preset tuning mechanism including a preset tuningshaft mounted for rotation about an axis parallel to the axes of saidslug, drive gear means mounted off-axis from said preset tuning shaftand shiftable between an engaged position for transmitting rotary motionbetween said preset tuning shaft and the slug gear means for the slug atsaid tuning position and a disengaged position, and means responsiveduring rotation of said tuning shaft in one direction for shifting saiddrive gear means to an axially forward engaged position and responsiveduring rotation of said tuning shaft in an opposite direction forshifting said drive gear means to an axially rearward engaged p0- sitionsuch that the slug gear means at said tuning position becomes disengagedwhen the corresponding slug reaches the end extreme corresponding tocontinued rotation of the tuning shaft in one direction and becomesreengaged when the tuning shaft is rotated in an opposite direction.

References Cited The following references, cited by the Examiner, are ofrecord in the patented le of this patent or the original patent.

UNITED STATES PATENTS 3,144,626 8/1964 Schwartz 334-51 3,058,075 10/1962Polley 334-51 3,148,345 9/1964 Moran 334-51 ELI LIEBERMAN, PrimaryExaminer U.S. Cl. X.R. 74-10.8

